[R] integrate function

[David Winsemius]

On Dec 5, 2009, at 4:59 PM, li li wrote:

> Hello,
>   I have some trouble in terms of using integrate function in R.
>
> f1 is a function of p and x where x is supposed to be a vector. (See  
> the
> code).
> Then I want to write function f2 which is a function of the vector
> x after I integrate out p.
>  Can some one give me some help? Many thanks!
>                             Hannah
>
>> f1 <- function (p,x)
> +   {
> +    y <- p*x+(1-p)*x^{2}
> +       prod(y)
> +   }
>>
>> f2 <- function(x)
> +     {
> +     integrate(f1, 0,1, x)

Just looking at the help page for integrate makes me wonder what you  
are doing. There are 3 named arguments before the dots, so 0 and 1  
will become "lower" and "upper", while x is not among the named  
arguemnts, so I suppose x will go to f1 as "p". But f1 takes two  
arguments, so where will it get the second argument? Maybe if you  
would tell us a bit more about why you made those functions the way  
you did, it would help. I am guessing it's classwork but perhaps not.


> +      }
>> f2(x=c(1,2))
> Error in integrate(f1, 0, 1, x) :
>  evaluation of function gave a result of wrong length
> In addition: Warning messages:
> 1: In p * x :
>  longer object length is not a multiple of shorter object length
> 2: In (1 - p) * x^{ :
>  longer object length is not a multiple of shorter object length
>
> 	[[alternative HTML version deleted]]

--

David Winsemius, MD
Heritage Laboratories
West Hartford, CT